This invention relates generally to rail vehicle power interconnection systems and more particularly to the sequential shifting between plural supply circuits.
In electric railway propulsion systems power is provided to the vehicle either by an on-board power plant or by a wayside power distribution system which is energized by stationary power plants located along the railway. Common methods of power distribution from the wayside include a third-rail-to-shoe combination and an overhead catenary-to-pantograph combination.
It is often desirable to use a power source having electrical characteristics of one type for one section of the railway and one having different characteristics for an adjacent section of the railway. For example, one section may require a d-c power source while the adjacent section may better be served by an a-c source, or it may be preferred to have either different voltages or different frequencies on the two sections. In any case it is necessary to provide a means of transitioning from one source to the other.
A simple method of accomplishing this is to provide a transition buffer zone between the two sections in which there is no power applied and through which the vehicle coasts. This is undesirable since the buffer zone must be at least as long as the train, and a shut down of the power for such a long period would disrupt the speed and efficiency of the train.
An alternative is to overlap the two power supply systems for a distance as great as or greater than the length of the train. During that period of time both sources are simultaneously available and power reconnection can be made in a brief interval. This is a workable solution where the transition is between a third rail and a catenary or vice-versa. However, where it is between two catenaries or two third rail sections, then paralleled collectors will cause a short between the two, resulting in a fault in the system.
It is therefore an object of this invention to provide for a smooth transition between two adjacent power sources to a rail vehicle.
Another object of this invention is the provision for disconnecting from a vehicle, a power source having one electrical characteristic and connecting one having another electrical characteristic.
Yet another object of this invention is the provision for transitioning between two incompatible power sources without any appreciable loss of vehicle speed.
Still another object of this invention is the provision for disconnecting and connecting imcompatible power sources to a vehicle in a proper sequence so as not to allow a short circuit between the two sources.
Another object of the invention is the provision of an automatic power transitioning system for operation with the vehicle traveling in either direction.
A further object of this invention is the provision for a power source transitioning system which is economical to manufacture and effective in use.
These objects and other features and advantages become more readily apparent upon reference to the following description when taken in conjunction with the appended drawings.